1. Field of the Invention
The present invention relates to a device for performing proper positioning when mounting a position sensor for an automatic transmission for automobiles or the like.
2. Description of the Related Art
A conventional position sensor for an automatic transmission has a change shaft which is interlocked with a shift lever. When the change shaft is rotated, a rotor within the position sensor is rotated so as to mechanically switch a connection of contacts between a moving contact and a plurality of fixed contacts which are previously provided corresponding to the number of shift positions. Then, the shift position is detected in accordance with a rotation angle when the rotor is rotated from a neutral position. (This system is called a switch type sensor.)
Accordingly, it is necessary to properly position the neutral position of the position sensor when mounted. Therefore, the position sensor is mounted with a positioning tool, for example.
Further, there are examples that reduce the number of the contacts by using a potentiometer (for example, see patent references 1 and 2).    Patent reference 1: Japanese patent laid-open publication No. H07-310823A.    Patent reference 2: Japanese patent laid-open publication No. 2002-120587A.
FIG. 11 is a view showing the positioning performed with the conventional positioning tool. A position sensor 100 is substantially in the shape of a fan. On a pivot portion of a casing 101 there is provided a boss 102 into which a hollow rotor shaft 103 is rotatably inserted. A change shaft 104 which is inserted into the rotor shaft 103 is fixedly fitted to the inside of the rotor shaft 103 in an integrally rotatable fashion. When the change shaft 104 is rotated, the rotor shaft 103 is integrally rotated and also a rotor 105 integrated with the rotor shaft 103 is rotated in the inside of the position sensor 100. Then, a moving contact provided on the rotor 105 comes into contact with a plurality of fixed contacts which are previously arranged on the same arc in accordance with each of the shift position, so that the shift position is switched in turn.
Each of the fixed contacts is arranged at a rotation angle using a neutral position of the rotor shaft 103 as the reference. This neutral position is properly positioned with a positioning tool 110 when the position sensor 100 is mounted on an automatic transmission (not shown).
The positioning tool 110 is provided with a positioning section 111. The positioning section 111 extends straight along a positioning reference line “L” which connects a rotation center of the rotor shaft and the moving contact and which is a straight line in the neutral position. The positioning section 111 is fitted into positioning grooves 106a, 106b formed on a surface of the casing 101, so that the position sensor 100 is positioned. Then, when mounting bosses 107a, 107b provided on two outer peripheral locations of the casing 101 are mounted by bolts 108a, 108b on the automatic transmission, the position sensor 100 is mounted on the automatic transmission in such a state that the neutral position is properly positioned.
In the above referred example using the potentiometer, the sensor is specialized in construction thereby to become complicated and expensive. Therefore, from the perspective of cost or the like, there are cases where it is desired to use the above referred switch type sensor. In the case of the switch type sensor, however, the high accuracy positioning of the neutral position is required at the time of mounting, and also it is necessary to check an electrical connection and to ensure an angle after mounting so that it takes much time and effort. This will be explained hereunder.
As shown in FIG. 8, each of the shift positions is arranged in the order of a parking position “P”, a reverse position “R”, a neutral position “N”, a drive position “D”, a fixed third speed position “D3”, a second position 2 and a low position 1. Fixed contacts corresponding to each of the shift positions are arranged on concentric circular arcs of a rotor shaft 103 and a change shaft 102 which have the common center “O”. The shift position is located on a central position of each of the fixed contacts. In the following explanation, reference characters of the shift positions are used with respect to the shift position (the central position of the fixed contact) and each of the fixed contacts.
Each of the fixed contacts is arranged at a predetermined angle with respect to the center (N-position) of an N-contact as the reference (0°). The angle from this N-position to each of the shift positions will be called a contact angle. Moreover, since the rotor shaft 103 and the change shaft 102 are integrally rotated such that the rotation of the rotor 105 causes the simultaneous rotation of the rotor shat 103 and the change shaft 102, such integral rotation will be called simply the rotation of the change shaft 102, in the following explanation.
Since at the time of mounting the position sensor 100, an electrical connection checking and an angle ensuring are not performed, the operation for the electrical connection checking and the angle ensuring is required after mounting. The electrical connection checking is performed for checking whether or not there is an electrical connection in each of the positions so as to detect whether or not there is anything unusual in the fixed contacts. On the other hand, the angle ensuring is performed for ensuring that, when shifted to the R-position or the D-position, the angle from the N-contact to an ON position of an R-contact or from the N-contact to an ON position of a D-contact falls within a predetermined range.
At first, when the change shaft 102 is rotated from the N-position to the P-position, whether there is the electrical connection at each of the P-position and the R-position is checked, and at the same time an angle α1 from an OFF position of the N-contact to the ON position of the R-contact is detected.
Next, when the change shaft 102 is rotated from the P-position to the 1-position in an opposite direction, the electrical connection is checked at each of the positions, and at the same time an angle β1 from the OFF position of the N-contact to the ON position of the D-contact is detected.
For positioning the position sensor 100, the N-position must be accurately fixed. For example, the angles α1 and β1 each require high accuracy and must be ensured within a predetermined tolerance of the order of 1/10°.
However, in the case where such high accuracy angle ensuring is required, the positioning method by the above positioning tool 100 takes much time and effort. Namely, when mounting the position sensor 100 while positioning it with the positioning tool 110, the setting of the positioning tool 110 is controlled by experience and skill or sense of the operator and a certain amount of variation exists in the setting operation, so that a certain amount of variation beyond the tolerance of the angle ensuring is unavoidably produced. Therefore, the additional operation for the electrical connection checking and the angle ensuring is required after the position sensor 100 is mounted. Moreover, in the case where the variation beyond the tolerance of the angle ensuring as above is produced, the bolts 108a, 108b are loosened once and fastened again while re-positioning the position sensor 100 with the positioning tool, and under certain circumstances this operation may be repeated several times.
Therefore, the present invention aims to make it possible to determine the neutral position in such a state that the angle is ensured before mounting the position sensor.